1. Field of the Invention
The invention relates to a method and apparatus for crystallizing tartar during the production of wine and removing the tartar in crystal form from the wine and more particularly to a method and apparatus for accelerating the crystallization of tartar.
2. Description of the Prior Art
Wine, and also champagne produced from wine, contain a salt formed in the grape during the growth that mainly consists of potassium hydrogen tartrate and will hereinafter be referred to as tartar. The content of tartar in grapes or grape must depends largely on the degree of ripeness of the grapes. Generally, as far as tartar is concerned, grape must represents a saturated or almost saturated solution of tartar. Solubility of tartar in must and in wine depends on a number of factors. The major factors include the alcohol content of the wine and the temperature. As soon as the grape must is subjected to fermentation and the formation of alcohol, the solubility of the tartar is lowered substantially. The original saturated solution after alcoholic fermentation provides a supersaturated solution of tartar. The surplus of tartar is removed by the formation of tartar crystals as soon as conditions are suitable. After elimination of the surplus tartar as crystals, each wine again represents a saturated solution of tartar.
Since the solubility of tartar in wine depends on temperature, a surplus of tartar will always develop if the wine is exposed to a lower temperature. The excess or surplus tartar is again eliminated through crystal formation as soon as suitable conditions are present. Further fermentation of wine to champagne decreases the solubility for tartar because of the renewed alcohol formation and, therefore, creates a new surplus of tartar.
The presence of tartar crystals in a bottle of wine is objected to by the buyer although the tartar crystals have no deleterious effect. Therefore, the wine producer is required to eliminate the tartar surplus during the production or processing stage of the wine so that tartar crystals are not present and will not form in closed bottles of wine.
Conventionally, the prevention of tartar formation in closed bottles is accomplished by cooling the wine for a long period of time, as for example five or ten days at a low temperature of -4.degree. or -5.degree. C. During that time, crystallization of the surplus tartar is more or less complete and the tartar crystals are separated from the wine by conventional separators or filters.
Another method of removing the tartar surplus is by cation exchange to render the insoluble surplus into soluble compounds. It is also possible, with the aid of electrodialysis, to remove the surplus of tartar from the wine.
The legal requirements for treating wine, the organoleptic properties such as taste and bouquet and commercial feasibility have to be considered in determining which method is to be employed for removal of the surplus tartar. The object of this invention is, therefore, to provide a method for tartar elimination from wine that is superior from the above-described processes. According to the invention, the surplus tartar is eliminated by means of reverse osmosis.
During the reverse osmosis, with the aid of high pressures against the direction of osmotic pressure, one forces the water or other easily permeating components of a solution through a semi-permeable membrane. For convenience, the portion that penetrates through the membrane will be referred to as the permeate, and the liquid portion retained by the membrane will be referred to as the concentrate.
With the aid of reverse osmosis, industrially ocean water or brackish water is prepared for drinking purposes. In the chemical industry, solutions are cleaned or purified by reverse osmosis and other solutions are concentrated. The interest is, therefore, either for the permeate, where the concentrate is rejected, or the interest is for the concentrate when the permeate is rejected.
It has been discovered that by reverse osmosis concentration the tartar crystals automatically develop and are present in the concentrate from which they can be easily eliminated. A procedure was developed from this observation to provide a new method of tartar elimination from wine by the use of reverse osmosis.